Tuesday, 29 November 2016

In
the Arctic, vast amounts of carbon are stored in soils that are now
still largely frozen. As temperatures continue to rise and soils
thaw, much of this carbon will be converted by microbes into carbon
dioxide or methane, adding further greenhouse gases to the
atmosphere.

In
addition, vast amounts of methane are stored in sediments under the
Arctic Ocean seafloor, in the form of methane hydrates and free gas.
As temperatures rise, these sediments can get destabilized, resulting
in eruptions of huge amounts of methane from the seafloor. Due to the
abrupt character of such releases and the fact that many seas in the
Arctic Ocean are shallow, much of the methane will then enter the
atmosphere without getting broken down in the water.

What
makes the situation so dangerous is that huge eruptions from the
seafloor of the Arctic Ocean can happen at any time. We can just
count ourselves lucky that it hasn't happened as yet. As temperatures
continue to rise, the risk that this will happen keeps growing.

This
dangerous situation has developed because emissions by people have
made the temperature of the water in the Arctic Ocean rise, and these
waters keep warming much more rapidly than the rest of the world due
to a number of feedbacks.One
such feedback is the retreat of the sea ice, which in turn makes the
Arctic Ocean heat up even more, as much sunlight that was previously
reflected back into space by the sea ice, instead gets absorbed by
the water when the sea ice is gone. Without
sea ice, stormscan
also develop more easily. Storms can mix warm surface waters all the
way down to the bottom of shallow seas, reaching cracks in sediments
filled with ice. This ice has until now acted as a glue, holding the
sediment together. As the ice melts, sediments can become
destabilized by even small differences in temperature and pressure
that can be triggered by earthquakes, undersea landslides or changes
in ocean currents.As
a result, huge amounts of methane can erupt from the seafloor of the
Arctic Ocean and once this occurs, it will further raise
temperatures, especially over the Arctic, thus acting as another
self-reinforcing feedback loop that again makes the situation even
worse in the Arctic, with higher temperatures causing even further
methane releases, in a vicious cycle leading to runaway global
warming.Such
a temperature rise in the Arctic will not stay within the borders of
the Arctic. It will trigger huge firestorms in forests and peatlands
in North America and Russia, adding further emissions including soot
that can settle on mountains, speeding up the melting of glaciers and
threatening to stop the flow of rivers that people depend on for
their livelihood. These
developments can take place at such a speed that adaptation will be
futile. More extreme weather events can hit the same area with a
succession of droughts, cold snaps, floods, heat waves and wildfires
that follow each other up rapidly. Within just one decade, the
combined impact of extreme weather, falls in soil quality and air
quality, habitat loss and shortages of food, water, shelter and just
about all the basic things needed to sustain life can threaten most,
if not all life on Earth with extinction.

How
much have temperatures risen and how much additional warming could
eventuate over the next decade? The image on the right shows a
potential global temperature rise by 2026 from pre-industrial levels.
This rise contains a number of elements, as discussed below from the
top down.

February
2016 rise from 1900 (1.62°C)The
magenta element at the top reflects the temperature rise since 1900.
In February 2016, it was 1.62°Cwarmer
compared to the year 1900, so that's a rise that has already
manifested itself.Rise
from pre-industrial levels to 1900 (0.3°C)Additional
warming was caused by humans before
1900. Accordingly,
the next (light blue) element from the top down uses 0.3°C warming
to reflect anthropogenic warming from pre-industrial levels to the
year 1900. When
also taking this warming into account, it was 1.92°C (3.46°F)
warmer in February 2016 than in pre-industrial times, as is also
illustrated on the image below.

Warming
from the other elements (described below) comes on top of the warming
that was already achieved in February 2016.Rise
due to carbon dioxide from 2016 to 2026 (0.5°C)The
purple element reflects warming due to the amount of carbon dioxide
in the atmosphere by 2026. While the IEA reported that energy-related
carbon dioxide emissions had not risen over the past few years,
carbon dioxide levels in the atmosphere have continued to rise, due
to feedbacks
that are kicking in,
such as wildfires and reduced
carbon sinks.
Furthermore, maximum warming occurs about one
decade after a carbon dioxide emission,
so the full warming wrath of the carbon dioxide emissions over the
past ten years is still to come. In conclusion, an extra 0.5°C
warming by 2026 seems possible as long as carbon dioxide levels in
the atmosphere and oceans remain high and as temperatures keep
rising.Removal
of aerosols masking effect (2.5°C)With
dramatic cuts in emissions, there will also be a dramatic fall in
aerosols that currently mask the full warming of greenhouse gases.
From 1850 to 2010, anthropogenic aerosols brought about a decrease of
∼2.53 K, says a recent
paper.
While on the one hand not all of the aerosols masking effect may be
removed over the next ten years, there now are a lot more aerosols
than in 2010. A 2.5°C warming due to removal of part of the aerosols
masking effect therefore seems well possible by the year
2026.Albedo
changes in the Arctic (1.6°C) Warming
due to Arctic snow and ice loss may well exceed 2 W per square meter,
i.e. it could more than double the net warming now caused by all
emissions by people of the world, calculated Professor
Peter Wadhams in 2012.
A 1.6°C warming due to albedo changes (i.e. decline of both Arctic
sea ice and snow and ice cover on land) therefore seems well possible
by the year 2026.Methane
eruptions from the seafloor (1.1°C)

Dr.
Natalia Shakhovaet
al. wrote in a paper presented at EGU
General Assembly 2008that "we
consider release of up to 50 Gt of predicted amount of hydrate
storage as highly possible for abrupt release at any time."
Authors calculated that such a release would cause 1.3°C
warming by 2100. This
1.3°C warming (by 2100) from an extra 50 Gt of methane seems
conservative when considering that there now is only some
5 Gt of methane in the atmosphere,
and over the next ten years this 5 Gt is already responsible for more
warmingthan
all the carbon dioxide emitted by people since the start of the
industrial revolution. Professor
Peter Wadhams co-authored a studythat
calculated that methane release from the seafloor of the Arctic Ocean
could yield 0.6°C warming of the planet in 5 years
(see videoat earlier
post). In
conclusion, as temperatures keep rising, a 1.1°C warming due to
methane releases from clathrates at the seafloor of the world's
oceans seems well possible by the year 2026 and even more warming
seems possible beyond that.

Extra
water vapor feedback (2.1°C)Rising
temperatures will result in more water vapor in the atmosphere (7%
more water vapor for every 1°C warming), further amplifying warming,
since water vapor is a potent greenhouse gas. Extrawater
vapor will result from warming due to the above-mentioned albedo
changes in the Arctic and methane releases from the seafloor that
could strike within years and could result in huge warming in
addition to the warming that is already there now. As the IPCC says:
"Water vapour feedback acting alone approximately doubles the
warming from what it would be for fixed water vapour. Furthermore,
water vapour feedback acts to amplify other feedbacks in models, such
as cloud feedback and ice albedo feedback. If cloud feedback is
strongly positive, the water vapour feedback can lead to 3.5 times as
much warming as would be the case if water vapour concentration were
held fixed",according
to the IPCC.
Given a possible additional warming of 2.7°C due to just two
elements, i.e. Arctic albedo changes and seafloor methane, an
additional warming over the next decade of 2.1°C due to extra water
vapor in the atmosphere therefore does seem well possible by the year
2026.

Further
feedbacks (0.3°C)Further
feedbacks will result from interactions between the above elements.
Additional water vapor in the atmosphere and extra energy trapped in
the atmosphere will result in more intense storms and precipitation,
flooding and lightning. Flooding can cause rapid decomposition of
vegetation, resulting in strong methane releases. Furthermore, plumes
above the anvils of severe storms can bring water vapor up into the
stratosphere, contributing to the formation of cirrus
cloudsthat
trap a lot of heat that would otherwise be radiated away, from Earth
into space. The number of lightning strikes can be expected to
increase by
about 12%for
every 1°C of rise in global average air temperature. At 3-8 miles
height, during the summer months, lightning activity increasesNOx
by as much as 90% and ozone by more than 30%. The combination of
higher temperatures and more lightning will also cause more
wildfires, resulting in emissions such as of methane and carbon
monoxide. Ozone acts as a direct greenhouse gas, while ozone and
carbon monoxide can both act to extend the lifetime of
methane. Additional
warming can also result from feedbacks that are currently holding
back warming, such as increased uptake of carbon by vegetation, which
a recent
studyattributes
to higher CO₂ levels in the atmosphere. This land sink now appears
to turn into a source of carbon emissions, due to deforestation and
soil degradation caused by agricultural practices and more extreme
weather, as discussed in this
post.

Until
recently, global warming was also thought to be held back due to
growth of sea ice around Antarctica and the resulting albedo changes.
Recently however, sea ice around Antarctica reached record low extent
for the time of the year (late 2016). On November 23, 2016, Antarctic
sea ice extent was 2.615 million km² smaller than it was on November
23, 2015.

To
put this 2.615 million km² in perspective, the minimum Arctic sea
ice in 1980 was 7.544 million km², and this minimum in 2012 was
3.387 million km², as illustrated by the image on the right.

In
conclusion, the joint impact from further feedbacks may well amount
to an additional 0.3°C warming by the year 2026, or much more than
that, cancelling out possible over-estimations in other
elements.

In
summary, adding up all the warming associated with the above elements
results in a total potential global temperature rise (land and ocean)
of more than 10°C or 18°F within a decade, i.e. by 2026. This
scenario assumes that no geoengineering will take place over the next
decade.

Accordingly,
this would lead to numbers of climate-related global deaths in line
with the prognosis below.